Flow-measuring device



Oct. 30, 1951 V, GENTLE, ,l 2,573,430

FLOWjMEASURING DEVICE Filed March 14, 1947 ATTORNEY Patented Oct. 30, 1951 UNITED sTATEs PATENT OFFICE FLOWMEASURING DEVICE Vincent Gentile, Jr., Brooklyn, N. Y.

Application March 14, 1947, Serial No. 734,785

-cient, and suitable for a wide range of fluidvelocity measurements.

It is another object to provide a device of the character indicated in which no special projections into the fluid stream are required.

Other objects and various further features of Athe invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings:

. Fig. 1 is a longitudinal sectional view of a fluidconducting member incorporating features of the invention;

Fig. 2 is a cross-sectional view taken in the plane 2-2 of Fig. l; and

Fig. 3 is a longitudinal sectional view of another embodiment of the invention.

In the present invention, viscous forces are used as the criterion of fluid velocity, and an introductory general discussion of principles may be helpful to a better understandingof the invention.

The tangential or boundary-layer resistance of the internal wall of a closed conduit carrying a uid is equal to S XF, in which S=area of wall surface in contact with the fluid,

and F=wallsurface resistance per unit of area.

SFT-25M in which- A=crosssectional area of the conduit, L=lcngitudinal length of the conduit, f=coe1iicient of friction,

V=mean stream velocity,

d=density of the fluid,

M=hydraulic radius, and g=gravitational constant.

Transposing Equation l, it follows that F- 2gMS It will be observed that for a given fluid all terms in the righthand part of Equation 2 are generally constant, with the exception of V. Even the exponent of V may be considered substantially constant at 2, at least for high Reynolds numbers. Equation 2 may, therefore, be rewritten as yF=Kv2 (a) in which K is a constant.

From Equation 3 it` follows that, the unit tangential drag is, in the region of turbulent flow in which my invention is to be employed. proportional to the square ofthe stream velocity; and differentials produced by surface drag at the boundary layer may, therefore, be expected to vary in a similar manner. Finally, since pressures produced by dynamic impact likewise vary as the square 0f the stream velocity, it should follow that differentials produced by a combination of viscous and dynamic forces are additive.

Briefly stated, my invention contemplates provision of a pressure-sampling passage in a conduit and inclined (at its opening to the inner wall of the conduit) with respect to the streamlines near the passage opening. In the specific forms to be described, one or a plurality of such openings are inclined to face in an upstream direction, and another one or a plurality of openings are inclined to face generally downstream; average upstream and average downstream pressures are collected, as by manifolds, and applied to a differential-pressure-indicating or measuring device.

Referring now to Figs. 1 and 2 of the drawings, my invention is shown in application to a pipe 5 of substantially constant internal diameter and in which there may be a fluid flow, say from left to right. In accordance with a feature of the invention, one or a plurality of generallyupstream-directed` passages 6-1-8 may be provid-ed in thev pipe 5,.a11 opening to the inner wall of pipe 5. In the event of a plurality of openings, such as those for passages 6-1-8, it is preferred that all the points where full passage area intersects the openings lie substantially in a single plane, normal to the axis of pipe 5; this normal plane'is indicated generally as 9 9 in Fig. 1. The pressures acting in passages 6--1-8 may be manifolded, as at I0, and fed, as an average pressure, to one side of a differentialpressure responsive device ii. In the form shown, the latter device is a common U-tube.

With the flow, as stated, from left to right. the total head impressed on the group of passages 6-1-8 pointing upstream should be equal 3 i to the static head in the system plus some component of the velocity head. In other words,

u: 2q l (4) in which H1 is the total head, s the static head, and Ic' a calibration constant.

It is clear that by providing an opening in pipe l normal to the axis thereof (and preferably in the plane 1 9), and by applying the static pressures impressed therein directly to the other arm of the U-tube Il, the pressure differential indicated would be a direct function of the stream velocity squared. I prefer, however, to

accentuate the differential indications by an apsaid passages into the pipe should lie in a` common normal plane and that this be plane l-S; all pressure samplings, upstream-directed and downstream-directed, may then be considered to be taken in the same plane 9 9.

Under the described conditions, that is, with flow from left-to-right, the downstream-directed passages IZ-IS-ll will be impressed with a total 'head equal to the static head minus some component of the velocity head. In symbols, this head H2 will be v2 5 2g y The differential head h available for flow measurement may then be expressed as Ah=H.-H.= (Maag (s.)

It will be seen that the inclined passages produce (in the turbulent region considered) differential pressures proportional to something approaching twice the velocity head in the system; by suitable calibration these differentials may be converted to read in any desired units ci.' flow.

In Fig. 3 I show a modification in which the principles of the invention are applied to a conduit or pipe i5 having a constricted passage, such as a throat i6 intermediate an inlet i1 and an outlet i8. The inner wall of the pipe I5 may converge generally uniformly frorn inlet I1 'to throat i6, andthe divergence from throat I6 to the outlet I8 may also be uniform. In accordance with the invention, an upstream-directed pressuresampling passage i9 (or a plurality thereof, circumferentially spaced, but not shown) opens to the inlet or converging part of the wall of pipe l5. The passage I9 may be substantially parallel to the axis of pipe l5 (as shown) but again it will be noted that at its opening in the inner wall, it is inclined with respect to flow streamlines adjacent the openings (which, of course, will be convergent in the region considered). A similar passage 2D (or a plurality thereof) may be provided to open onto the diverging part of the inner wall. The passages i9-20 may, as in the case of Fig. l arrangement, be separately manifolded 4 for attachment to a U-tube or other differentialpressure-responsive device, as will be clear.

The principles applied in the discussion of pressure heads operating in the Fig l arrangement will be understood to apply with similar eiectiveness for the system of Fig. 2. 'I'he essential difference between differentials derived by the two systems is that in the unrestricted' case (Fig. l) the available pressures are probably those due substantially only to viscosity, whereas in the case of a constriction, such as the throat I6, pressures are likely to be the result of a combination of viscous and dynamic forces.

It will be appreciated that I have described a relatively simple flow-measuring device for the measurement of static and velocity pressures of moving fluids. 'I'he device may be easily fabricated and machined, and scale models may be reproduced with accuracy, thus simplifying calibration. If the pressure-sampling passages are inclined at substantially the same angles on opposite sides of a plane normal to the conduit axis. the device may be used for flow measurements in either direction, for with a reversal of ow only the sign of the differential is changed.

In the constant-diameter case (Fig. l) expansive gases and vapors may be metered with the same facility as liquids, for theusual correctionsv y (to account for changes in internal energy due to expansion) drop out of the complex adiabatic equation; this arrangement may also be particularly useful in fire-line meters, which are frequently specified to provide an unrestricted ilow passage. With suitable design oi' the outer contours of the conduit, my invention may be employed as a speed-indicating device for moving craft, such as ships or airplanes, immersed in the free waterstream or airstream, as the case may be. The Fig. 3 arrangement shows in general that such an application may readily be made for either of the internal arrangements of passages of Figs. l or 3. In the form shown, a streamlined sleeve 2| embraces and closes off the recesses 22-23, which then deiine the pressure manifolds, and a streamlined strut 24 is provided with internal passages 25--26 to conduct the manifolded pressures to the diiferential-indieating equipment.

Whether or not the above statements of theory are correct, it is a fact that devices constructed in accordance with the present description have been observed to function generally as stated.

While I have described my invention in detail for the preferred form shown, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

I claim:

l. In apparatus of the character described, a tube having an internal bore providing a passage for the flow of fluid relative to said tube, said passage being substantially'unobstructed within the inner surface of the surrounding tube wall, means for transmitting through the wall of said tube pressures corresponding to viscous forces at the inner surface of said wall during flow of said fluid through said flow passage, said means comprising a pressure-sampling passage in said tube wall' and opening at one end into said iiow passage at the inner surface of said wall, the axis of said pressure-sampling passage at said open-A ing being inclined at an angle of the order of with respect to a plane normal to the ilow streamlines near said opening, and means communicating with the other end of said pressurepassage being substantially unobstructed within the inner surface of the surrounding tube wall. means for transmitting through the wall of said tube pressures corresponding to viscous forces atthe inner surface of said wall during iiow of said fluid through said flow passage. said means comprising two pressure-sampling passages in said tube wall, each of said pressure-sampling passages opening at one end into said flow passage at the inner surface of said wall, the axis oi one of said pressure-sampling passages at the opening thereof into said tube being inclined at an angle of the order of 85 with respect to a plane normal to the ilow stream lines near said opening, and the axis of the other of said pas-- sages at the opening thereof into said tube being inclined in the opposite direction to the rst passage and at an angle to a plane normal to the iiow stream lines near said opening of said other passage, and means communicating with the other ends of said pressure-sampling passages for connecting the same to a manometer.

3. In a measuring device oi the character indicated, a pipe having a ilrst plurality of passages opening to the inner wall of said pipe `and inclined to a plane normal to the axis thereof, said pipe having a second plurality oi passages inclined in an opposite direction to said normal plane and opening 'into the inner wall of said pipe,y the parts-of said openings which comprise full sections of said es all lying substantially in said plane. Y x

4; A device according to claim 3, wherein said passages are inclined at angles oi' the order of 85 with respect to said normal plane,

5. In a measuring device of the character indicated,`a pipe having a first plurality o1 passages opening to the inner wall oi said pipe and inclined at angles of the order of 85 to a plane normal to the flow stream lines at said openings,

said pipe also having a second plurality of passages opening to the inner wall of said pipe, said second passages being inclined to a plane normal to the iiow stream lines at the openings ofv said second passages and in the opposite direction to the inclination oi the first-mentioned passages.

6. Apparatus as deiined by claim 2, wherein said passage for the iiow of duid converges from an inlet to a throat and diverges from said throat to an outlet, and wherein one of said pressure sampling passages opens to the converging part of said ow passage and the other of said pressure-sampling passages opens to the diverging part of said ilow passage.

7. Apparatus as defined by claim 6 wherein said pressure-sampling passages at their openings to said ow passage are substantially parallel to the axis of said tube.

, 8. Apparatus as deiined by claim 2, wherein the internal bore providing a passage for the ilow of fluid is formed by a throated inner wall in which the minimum cross-sectional area is less than that of the inlet or outlet oi said tube. and wherein the iirst o1 the pressure-sampling passages opens to said wall at one side of the point of minimum cross-sectional area, the second of said pressure-sampling passages opening to another part of said wall.

VINCENTGENTILE, Jn.

REFERENCES CITED 'lhe kfollowing references are of record in the le, of this patent:

UNITED STATES PATENTS Number Name Date 749,645 Tuttle Jan. 12, 1904 944,417 Connet ,Dec. 28, 1909 1,627,896 Hanson May 10, 1927 v 1,946,319 Hodgson Feb. 6, 1934 2,065,789 Bolsinger Dec. 29, 1936 FOREIGN PATENTS Number Country Date 287,478 Great Britain July 26, 1928 

